In the present study, the effect of the pairing interaction and the isovector correlation between nucleons on the properties of the isobar analog resonances (IAR) in 112−124 Sb isotopes and the isospin admixture in 100−124 Sn isotopes is investigated within the framework of the quasiparticle random phase approximation (QRPA). The form of the interaction strength parameter is related to the shell model potential by restoring the isotopic invariance of the nuclear part of the total Hamiltonian. In this respect, the isospin admixtures in the 100−124 Sn isotopes are calculated, and the dependence of the differential cross section and the volume integral J F for the Sn( 3 He,t)Sb reactions at E( 3 He)= 200 MeV occurring by the excitation of IAR on mass number A is examined. Our results show that the calculated value for the isospin mixing in the 100 Sn isotope is in good agreement with Colo et al.'s estimates (4 − 5%), and the obtained values for the volume integral change within the error range of the value reported by Fujiwara et al. (53±5 MeV fm 3 ). Moreover, it is concluded that although the differential cross section of the isobar analog resonance for the ( 3 He,t) reactions is not sensitive to pairing correlations between nucleons, a considerable effect on the isospin admixtures in N ≈ Z isotopes can be seen with the presence of these correlations.
The ω-meson photoproduction, γ + p → p + ω, is studied in the framework of a model, containing π-meson exchange in t-channel and nucleon-exchange in s-and u-channels. Considering both ωN N -coupling constants in the region of time-like meson four momenta as the free parameters, we find different sets of solutions for these constants from the existing data on the t-dependence of the differential cross sections, dσ(γ + p → p + ω)/dt, in the near threshold region E γ ≤ 2 GeV. These sets of ωN N -coupling constants, corresponding to destructive and constructive π N -interference contributions to dσ/dt can be well distinguished by measurements of beam asymmetry, induced by linear photon polarization.
The Gamow-Teller (GT) transition is inarguably one of the most important nuclear weak transitions of the spin-isosopin στ type. It has many applications in nuclear and astrophysics. These include, but are not limited to, r-process β-decays, stellar electron captures, neutrino cooling rates, neutrino absorption and inelastic scattering on nuclei. The quasiparticle random phase approximation (QRPA) is an efficient way to generate GT strength distribution. In order to better understand both theoretical systematics and uncertainties, we compare the GT strength distributions, centroid and width calculations for 40−60 Ti isotopes, using the pn-QRPA, Pyatov method (PM) and the Schematic model (SM). The pn-QRPA and SM are further sub-divided into three categories in order to highlight the role of particle-particle (pp) force and deformation of the nucleus in the GT strength calculations. In PM, we study only the influence of the pp force in the calculation. We also compare with experimental results and other calculations where available. We found that the inclusion of pp force and deformation significantly improves the performance of SM and pn-QRPA models. Incorporation of pp force leads to pinning down the centroid value in the PM. The calculated GT strength functions using the pn-QRPA (C) and SM (C) models are in reasonable agreement with measured data.
In this study, based on Pyatov-Salamov method, the properties of the Gamow-Teller(GT) 1 + states in 90 Nb have been investigated and the agreement of our results calculated by this method for the energy of Gamow-Teller Resonance (GTR) and the corresponding strengths of the 1 + excitations in 90 Nb with the experimental values has been tested. As a result of the calculations, it was seen that the calculated values for the energy and strength of the GTR are sufficiently in agreement with the experimental ones.
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